SAPROPHYTES AND PARASITES 79 



apex when mature, and then globose and warted. This stage 

 was formerly known as Aecidium violae. Before either sper- 

 mogonia or aecidia appear there is always present a plentiful 

 mycelium in the tissues. The swelling of the petioles is caused 

 by the development of this mycelium, the cluster-cups being 

 developed from the same mycelium as the spermogonia, and 

 consequently deeply innate and thoroughly endophytal. The 

 mature aecidiospores, after voluntary separation from the chain, 

 will germinate within a few hours, but seldom after a period 

 of forty -eight hours. Each spore has severalgerm-pores, 

 perhaps four or six, but germination seldom proceeds from 

 more_than one. _ This cylindrical tube continues growing until 

 it has acquired a considerable length,, the coloured contents of 

 the spore passing meantime _ along the tube to its extremity, 

 which finally enters one of the stomata of the proper host- 

 plant, and there, by branching and progressive growth, con- 

 s'tftutes"a mycelium, presumably the mycelium which becomes 

 the spore-bed of the uredospores. If we return to the violet 

 leaves later in the year, we shall find the under surface 

 of . many leaves exhibiting small raised pustules, which are 

 scattered ail over the surface. These sori, or pustules of the 

 Uredo,-' are soon exposed by the irregular splitting of the 

 cuticle, and the light brown spores, resembling snuff, are freely 

 distributed. Examined more closely, each pustule will be 

 found to possess a spore -bed of compacted mycelium, from 

 which the uredospores grow, at the apices of rather short 

 hyaline threads or peduncles, which are soon absorbed, leaving 

 an elliptical pale-brown spore, with a shortly spinulose surface, 

 . as the second stage of an alternation of generations, the problem- 

 atic spermatia being left out of the question. It must be remem- 

 bered that the origin of an uredospore-bed is not absolutely 

 resultant from a germinating aecidiospore, but it may also be 

 produced by a germinating uredospore, or by the germination 

 of a promycelial spore. This fact may be associated with the 

 other fact, that some species of Puccinia are known with which 

 no aecidium has yet been associated. Tiie-matur>e_ uredospores 

 have two, three, or four points of germination or germ-pores. 

 The germination . takes - place,~as in the 'aecidiospores, -within a 

 few hours, and in like manner the growing point enters one 



